In recent years, an elevator having a rated speed for ascent of a car, which is set higher than that for descent, has been proposed. A conventional speed governor used for such an elevator includes a clutch mechanism provided between a governor sheave rotated by running of the car and a rotary body which is rotated by transmission of the rotation of the governor sheave. The clutch mechanism transmits the rotation from the governor sheave to the rotary body when the car descends, whereas the clutch mechanism interrupts the transmission of the rotation from the governor sheave to the rotary body when the car ascends. Moreover, a mechanism for detecting an excess of a running speed when the car descends is mounted to the rotary body. Further, a mechanism for detecting the excess of the running speed when the car ascends is mounted to the governor sheave (for example, see Patent Document 1).    Patent Document 1: JP 2000-327241 A